The bone morphogenetic proteins (BMPs) are involved in a variety of developmental and differentiation processes in skin and hair, heart, kidney, reproductive tissues, neural tissues and cartilage, bone and tooth development. In this application, the investigators' major goal is to characterize the mechanisms by which transcription of the BMP2 and BMP4 genes are regulated in osteoblasts and other tissues in vivo and to examine the mechanisms by which BMP2 affects osteoblast function. The stated goals are: 1. To extend prior studies on BMP effects on osteoblasts and chondroblasts and in particular to identify homeobox and other mRNA species which are regulated by BMP2 and which may regulate BMP2 and BMP4 expression during differentiation. 2. To characterize transcriptional regulation of the BMP2 and BMP4 genes in vivo, they will use transgenic mice in which BMP2 or BMP4 gene fragments from the 5' flanking region and other regions are linked to bacterial beta-galactosidase (LacZ) and/or luciferase (LUC). BMP2 and 4 gene transcription control will be examined. Using these mice, genetic crosses to candidate mutant mice can be established to evaluate gene networks and interactions with the BMP2 and BMP4 genes. 3. Using specific regions of the BMP4 promoter driving human BMP4 cDNA that directs expression in the normal BMP4 domains of 6.5-8.5 dpc embryos, the investigators will attempt to rescue the BMP4 homozygous null mutant phenotype. New phenotypes may develop that will give insight into the role of BMP4 later in development.